The electrical industry uses a variety of dielectric fluids which are easily available and generally cost effective. Examples are mineral oil, silicone fluid, and synthetic hydrocarbon oils used in transformers, power cables and capacitors. Such fluids must be electrically insulating, resistant to degradation, and be able to act as a heat transfer medium so that heat generated in an electrical apparatus can be dissipated to the surrounding environment.
However, currently used fluids also have several deficiencies. Many of these fluids are not considered to be biodegradable in a reasonable time frame. Some have electrical properties which render them less than optimal. In recent years regulatory agencies have become increasingly concerned about oil spills which can contaminate the ground soil and other areas. A biodegradable dielectric fluid would be desirable for electrical apparatus such as transformers used in populated or ecologically sensitive areas.
U.S. Pat. No. 6,160,144 relates to synthetic esters of alcohols and fatty acid mixtures containing at least 85% by weight of oleic acid and 0.5 to 2.5% by weight of stearic acid and to their use as lubricants and hydraulic oils and for cosmetic purposes.
U.S. Pat. No. 6,278,006 discloses oils containing a triacylglycerol polyol ester and a non-glycerol polyol ester, as well of methods of making such oils and methods for improving lubrication properties of a vegetable oil.
U.S. Pat. No. 7,048,875 relates to a high oleic oil composition useful as an electrical insulation fluid, to electrical insulation fluid compositions, and electrical apparatuses which comprise the same. Disclosed are the electrical properties of high oleic acid triglyceride compositions that comprise fatty acid components of at least 75% oleic acid, less than 10% diunsaturated fatty acid component; less than 3% triunsaturated fatty acid component; and less than 8% saturated fatty acid component. In some preferred embodiments, the electrical insulation fluid comprises fatty acid components of: at least 75% oleic acid, less than 10% linoleic acid, less than 3% linolenic acid, less than 4% stearic acid, and less than 4% palmitic acid.
Published Canadian Patent Application CA 2,492,565 discloses a dielectric coolant having at least a pour point of about −40° C. and comprising a mixture of more than one polyol ester of specified chemical structures, wherein the alkyl groups have chain lengths of C5 to C22. Neopentyl glycol and trimethylolpropane are disclosed as preferred polyols.
There is a continuing need for biodegradable dielectric fluids having good oxidative stability. There is an ongoing need for electrical apparatuses which comprise a biodegradable dielectric fluid having good oxidative stability. There is a need for a process to prepare biodegradable dielectric fluids having good oxidative stability.